inventory + variety = success

[mstechca]

Yes, I'm taking again :lol:
Zach, you and I are in competition. Maybe I talk too much :shock:

Anyways, I have learned that an inventory with a large variety creates success. Here's why:

I tried to create myself an R/2R ladder, and I did violate one rule by using 270K resistors instead of 240K resistors, because I had 10 270K resistors, and no 240K's. I have over 100 120K resistors, so I used them in my ladder.

The rule for my ladder is to use 120K and 240K resistors as R and 2R respectively.

Now I have to go BUY 240K resistors because I have all resistance values BUT 240K. Not only that, I can't find a resistor that is double of one other resistor.

I have to use 240K instead of two 120K's in series because I have already made my PCB and drilled holes in it.

So, without a great inventory, expect poorer circuits!

 

[zachtheterrible]

Yup. I just had to use 3 1/2watt 10k resistors because I ran out of 1/4 watt :lol: . Now my PIC programmer looks even worse. I had to build it on veroboard because I am temporarily out of presensitized board, there are wires running everywhere! :lol: Again, lack of inventory.

I've been thinking about taking one of my paychecks and blowing it all on getting SMT stuff, and a ton of general components so that I can have a really good inventory. It would be great to have SMT parts so I could make my circuits smaller. Maybe after I pay my whopping insurance bill for this year :lol:

 

[mstechca]

Again, lack of inventory.

We all must have that from time to time :lol:

I've been thinking about taking one of my paychecks and blowing it all on getting SMT stuff, and a ton of general components so that I can have a really good inventory. It would be great to have SMT parts so I could make my circuits smaller. Maybe after I pay my whopping insurance bill for this year :lol:

OMG :shock:
You must have turned 16 and started your driving lessons :shock: :lol:
That must be why your insurance bill is so whopping.

I can't even spend a whole paycheck on electronics because my rent and my (older) family cost too much.

 

[akg]

Now I have to go BUY 240K resistors because I have all resistance values BUT 240K. Not only that, I can't find a resistor that is double of one other resistor....

i donot think u can get a resistor(carbon) of that value , carbon res: series does not include that AFIAK. R+(r+r) is the best u can use

 

[audioguru]

My parts inventory is also beginning to get low. If my capacitor or resistor drawer is empty then I look through my old projects and tonnes of electronic junk I have (good stuff). Usually I steal nice little capacitors and tiny 0.1W resistors from them. My solder-sucker can rip out a part in no time, usually the sucked-on parts fall out. :lol:

 

[bryan1]

A good tip I found for scrounging parts off an old circuit board is a heat gun. A quick blow and a tap on the back off the board and most of the parts just fall off. I only wish I found this out before as I've gone thru 2 soldering irons and heaps of tins of butane in the past. Now if I need a part I look in one of the boxes where I've put all the scrounged parts as the nearest electronics shop is a hour drive each way.

Cheers Bryan

 

[Roboticinfo]

Again, lack of inventory.

We all must have that from time to time :lol:

I've been thinking about taking one of my paychecks and blowing it all on getting SMT stuff, and a ton of general components so that I can have a really good inventory. It would be great to have SMT parts so I could make my circuits smaller. Maybe after I pay my whopping insurance bill for this year :lol:

OMG :shock:
You must have turned 16 and started your driving lessons :shock: :lol:
That must be why your insurance bill is so whopping.

I can't even spend a whole paycheck on electronics because my rent and my (older) family cost too much.

Zach is 17 or 18 now

 

[mstechca]

Now I have to go BUY 240K resistors because I have all resistance values BUT 240K. Not only that, I can't find a resistor that is double of one other resistor....

i donot think u can get a resistor(carbon) of that value , carbon res: series does not include that AFIAK. R+(r+r) is the best u can use

Sayal Electronics sells 240K's, and that is where I am going.

Even if they didn't have 240K's, I could probably get away with a 56K or a 62K, but the ADCER (Audioguru's Defined Circuit Error Rate :lol: ) is higher.

 

[audioguru]

240k is a standard 5% value for carbon film and metal film resistors.
Since they are plus or minus 5%, they could be anywhere from 228k to 252k. The 120k resistors could be anywhere from 114k to 126k so the combination could be way off.

ADC chips also have resistances with poor tolerances but their ratios are nearly perfect. Their low error is rated in a few parts per million. :lol:

 

[zachtheterrible]

Yup, i'm 17. fortunately we got pretty cheap insurance so it's not so bad :lol:

bryan, ill have to give that a shot, you probably remember my taking parts off with a propane torch. works great, but being able to tap the board and most of the parts falling off would be sweet! :lol:

 

[akg]

240k is a standard 5% value for carbon film and metal film resistors.

i thought only multiples(*10) of 1,1.2,1.5,1.8,2.2,2.7,3.3,3.9,4.7,5.6,6.8,8.2 are there with carbon film resistor :?

 

[Nigel Goodwin]

240k is a standard 5% value for carbon film and metal film resistors.

i thought only multiples(*10) of 1,1.2,1.5,1.8,2.2,2.7,3.3,3.9,4.7,5.6,6.8,8.2 are there with carbon film resistor :?

That's the E12 series (12 values), the E24 series (24 values) is common as well.

As mstechca is trying to build a 10 bit D2A (with slightly better than 0.1% accuracy) and using only 5% resistors, the entire design seems doomed to failure (or at least extremely poor performance).

 

[bryan1]

HeHeHe it's good to see a pro take down a big mouth amateur good onya Nigel :twisted: But this is a **** chat section so I can play around. No offence Mcensha or what ever your name is :twisted: :twisted: :twisted:

 

[audioguru]

It seems that the 5% resistors I buy from reputable manufacturers are taped in a string and are all nearly the same value, up to 5% high or 5% low.
But the resistors I remove from cheap Chinese junk are always spot-on.
Do the Chinese make resistors with better accuracy than everyone else? :?:

The "surplus" resistors that MStechca and I buy from Sayal are probably made in India and maybe are rejects, since their values measure all over the place!

 

[bloody-orc]

all the resistors i buy from ELFA are also kinda spot on. if i buy 120k i get 120k +-1k max.

 

[mstechca]

As mstechca is trying to build a 10 bit D2A

I decided to step down to an 8-bit DAC.

...using only 5% resistors, the entire design seems doomed to failure (or at least extremely poor performance).

I played with 120K and 270K resistors, and the DAC is a complete failure (obviously). With 240K resistors, I will get better results. In fact, I'll use my ohmmeter to measure each and every single one.
I have not found a single resistor that is the exact value, but I have found a couple of 5% ones that measure 1% off.

The 200 pack I bought were all on a string, and according to Talkingelectronics.com, If I took two resistors from one string, the values will be nearly the same. If I took them from two different strings, the values could be way off.

HeHeHe it's good to see a pro take down a big mouth amateur

Big mouth amateur? Did you try my transmitter circuit in the projects section yet? It works very nicely, and I thought of it myself!

good onya Nigel

No one compares to him and audioguru, so I think we all are amateurs!

No offence Mcensha or what ever your name is

MStechca is my USER ID.
My real name is Mike.

and here's the breakdown of my name:

Mike
S (it stands for my last name which I do not want to reveal)
Technologies
Canada

I tried to design a name for a business and MS Technologies Canada was the very first name that rolled off my toungue
:lol:

 

[audioguru]

MStechca,
It looks like I am the only one to spell your user ID correctly. :wink:

 

[Nigel Goodwin]

MStechca,
It looks like I am the only one to spell your user ID correctly. :wink:

Including him? - I copied and pasted it from his posts 8)

On a more electronics theme, an 8 bit R2R ladder still needs better than 0.5% tolerance resistors.

 

[zachtheterrible]

Wow, I just realized that mstechca's name has another C in it. I've alwas spelled it mstecha :lol:

 

[eblc1388]

The 200 pack I bought were all on a string, and according to Talkingelectronics.com, If I took two resistors from one string, the values will be nearly the same. If I took them from two different strings, the values could be way off.

I once measured 1,000 resistors on a tape trying to get several resistors of the same value. The result I found they all randomly distributed around the +/- 4% rated value. I then wrote down their values on the tape so I can pick the value I wanted later.

So it is definitely not true that resistors on a string is of nearly the same value.